Cooperation of Murine F1 T and Parental B Lymphocytes in Rejection of a Xenogeneic Tumour: Adaptive Differentiation of B Lymphocytes?

The primary humoral immune response to rat Yoshida ascites sarcoma (YAS) grown in mice was used to study thymus-dependent (T) and bone marrow-derived (B) lymphocyte cooperation. It was shown that B6D2F₁ T lymphocytes that do not cooperate with parental B lymphocytes enabled parental B lymphocytes from B6→B6D2F₁ radiation chimaeras to reject the tumour. However, when the bone marrow cells from B6→B6D2F₁ chimaeras were used to reconstitute parental B6 mice, these B6→B6D2F₁→B6 mice lost their tolerance to D2 transplantation antigens, and their B lymphocytes were not able to cooperate with B6D2F₁ T lymphocytes. In our search for the reasons for the failure of F, T cells to be effective in parental and P→F₁→P TIR mice, rejection of F₁ T cells was excluded because; (i) immune reactivity in TIR mice was found to be either absent or minimal: (ii) parental TIR mice did not produce any detectable cytotoxic anti bodies after an intra venous injection of F₁ splenic T cells; and (iii) YAS rejection was not induced at very high doses of F₁ T cells. However, in a cell transfer system we were able to demonstrate that injection of spleen cells from parental TIR mice could thwart the successful cooperation of transferred F₁ T cells with host B cells. Collectively, these data suggest that the changes of the collaborative potential of parental B cells as achieved in the F₁ environment could he ascribed to ‘adaptive’ differentiation of B lymphocytes. It appears that the differentiation process that has rendered nonsyngeneic chimaeric cells able to cooperate was independent of the exogenous antigen. [ABSTRACT FROM AUTHOR]